Imaging element, solid-state imaging device, and electronic device

ABSTRACT

An imaging element has a laminated structure including a first electrode, a light-receiving layer formed on the first electrode, and a second electrode formed on the light-receiving layer. The second electrode is made of a transparent amorphous oxide having a conductive property.

TECHNICAL FIELD

This disclosure relates to an imaging element, a solid-state imagingdevice, and an electronic device.

BACKGROUND ART

An imaging element constituting an image sensor and the like has astructure of, for example, interposing a light-receiving layer (aphotoelectric conversion layer) by two electrodes. Such imaging elementincludes a transparent electrode to which light enters usuallyconstituted of a crystalline ITO. However, such transparent electrodehas a large internal stress. This generates stress damage to thelight-receiving layer, often deteriorating a characteristic of theimaging element. An imaging element (a photoelectric conversion element)to solve such problem caused by the internal stress from the transparentelectrode has been well-known from, for example, Japanese PatentApplication Laid-Open No. 2010-003901. That is, the imaging element (thephotoelectric conversion element) disclosed in this patent publicationincludes a photoelectric conversion layer, which is disposed between apair of electrodes, and at least one stress buffer layer, which isinterposed between one of the pair of electrodes and the photoelectricconversion layer.

The stress buffer layer has a laminated structure including crystallinelayers, specifically, a structure that laminates each two layers of thecrystalline layers and amorphous layers (four layers in total) inalternation.

CITATION LIST Patent Document

-   Patent Document 1: Japanese Patent Application Laid-Open No.    2010-003901

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, according to the technique disclosed in the above-describedpatent publication, the stress buffer layer has at least four-layerconstitution; therefore, the structure is complex. This makes aformation process complex and causes a problem of requiring long time toform the stress buffer layer.

Accordingly, an object of the present disclosure is to provide animaging element that is less likely to generate stress damage in alight-receiving layer and the like while having a simple structure, asolid-state imaging device that includes this imaging element, and anelectronic device.

Solutions to Problems

An imaging element of the present disclosure for achieving the aboveobject includes a laminated structure including a first electrode, alight-receiving layer formed on the first electrode, and a secondelectrode formed on the light-receiving layer, wherein the secondelectrode is made of a transparent amorphous oxide having a conductiveproperty.

A solid-state imaging device of the present disclosure for achieving theabove object includes a plurality of imaging elements, wherein theimaging elements each have a laminated structure including a firstelectrode, a light-receiving layer formed on the first electrode, and asecond electrode formed on the light-receiving layer, and the secondelectrode is made of a transparent amorphous oxide having a conductiveproperty.

An electronic device of the present disclosure for achieving the aboveobject includes a laminated structure including a first electrode, alight-emitting/light-receiving layer formed on the first electrode, anda second electrode formed on the light-emitting/light-receiving layer,wherein the second electrode is made of a transparent amorphous oxidehaving a conductive property.

Effects of the Invention

With an imaging element of the present disclosure, an imaging elementconstituting a solid-state imaging device of the present disclosure, andan electronic device, since a second electrode is transparent and has aconductive property, this allows incident light to reliably reach alight-receiving layer or a light-emitting/light-receiving layer.Moreover, since the second electrode is made of amorphous oxide,internal stress at the second electrode decreases. Therefore, evenwithout forming a stress buffer layer with complex configuration andstructure, stress damage is less likely to occur in the light-receivinglayer or the light-emitting/light-receiving layer during formation ofthe second electrode, free from a deterioration of characteristic of theimaging element and the electronic device. Further, since the secondelectrode is made of the amorphous oxide, a sealing property isimproved. Consequently, compared with the case of configuring the secondelectrode with a transparent electrode with conventional crystalline,this feature ensures restraining unevenness in sensitivity in theimaging element and the electronic device. Note that the advantageouseffects described in this description are merely an example and are notlimited. Additionally, an additional advantageous effect may beprovided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A and FIG. 1B are schematic, partial cross-sectional views of asubstrate and the like to describe a method for manufacturing an imagingelement and the like of a first embodiment. FIG. 1C is a schematic,partial cross-sectional view of an imaging element and the like of asecond embodiment.

FIG. 2 is a graph illustrating an example of results of obtaining arelationship between an amount of introduced oxygen gas (oxygen gaspartial pressure) and a value of a work function of a second electrodewhen a second electrode is formed by a sputtering method in the firstembodiment.

FIG. 3A and FIG. 3B are graphs of I-V curve each obtained from theimaging elements and the like of the first embodiment and a firstcomparative example. FIG. 3A illustrates measurement results of a lightcurrent, and FIG. 3B illustrates measurement results of a dark current.

FIG. 4A and FIG. 4B are each conceptual diagrams for energy diagram ofthe imaging element and the like of the first embodiment and the firstcomparative example. FIG. 4C and FIG. 4D are each conceptual diagramsillustrating a correlation between a difference in a value of the workfunction and the energy diagram of the imaging element and the like ofthe first embodiment and the first comparative example.

FIG. 5 is a graph illustrating results of examining a relationshipbetween an oxygen gas partial pressure and an internal stress in alaminated structure during formation of the second electrode of thefirst embodiment.

FIG. 6A and FIG. 6B are charts each illustrating results of X-raydiffraction analysis of the second electrode of the first comparativeexample and the first embodiment.

FIG. 7 is a conceptual diagram of a solid-state imaging device of athird embodiment.

FIG. 8 is a diagram illustrating a configuration of the solid-stateimaging device of the third embodiment.

FIG. 9A is a graph illustrating measurement results of an amount of warpof a laminated structure formed of a silicon semiconductor substrate, anLTO film, and a transparent conductive material. FIG. 9B is results oftaking images of the imaging element with the second electrodeconstituted of an IZO film and an ITO film and scanning electronmicrographs of a surface of the second electrode.

MODE FOR CARRYING OUT THE INVENTION

The following describes the present disclosure on the basis ofembodiments with reference to drawings. However, the present disclosureis not limited to the embodiments, and various values and materials inthe embodiments are examples. Note that the following gives theexplanation in the following order.

1. General Explanation on Imaging Device and Electronic Device ofPresent Disclosure 2. First Embodiment (Imaging Device and ElectronicDevice) 3. Second Embodiment (Modification of First Embodiment)

4. Third Embodiment (Solid-State Imaging Device of This disclosure)

5. Others <General Explanation on Imaging Device and Electronic Deviceof Present Disclosure>

With the imaging element of the present disclosure, the imaging elementin the solid-state imaging device of the present disclosure, and theelectronic device of his disclosure, when 0 bolts are applied between afirst electrode and a second electrode, a value of a dark currentflowing between the first electrode and the second electrode is assumedas J_(d-0) (ampere), and when 5 bolts are applied between the firstelectrode and the second electrode, a value of the dark current flowingbetween the first electrode and the second electrode is assumed asJ_(d-5) (ampere). Then, a form meeting: 0.8≦J_(d-5)/J_(d-0)≦1.2 can beconfigured. Additionally, when a voltage exceeding 0 bolts to 5 bolts orless is applied between the first electrode and the second electrode, avalue of the dark current flowing between the first electrode and thesecond electrode is assumed as J_(d) (ampere), 0.8≦J_(d)/J_(d-0)≦1.2 ismet. Here, the dark current can be obtained in a state where light isnot irradiated, specifically, by measuring a current flowing between thefirst electrode and the second electrode when a reverse-bias voltage isapplied between the first electrode and the second electrode under astate of dark place.

With the imaging element of the present disclosure, the imaging elementin the solid-state imaging device of the present disclosure, or theelectronic device of the present disclosure including theabove-described preferable forms, a laminated structure is preferablyhas a form of having internal stress, compressive stress of 10 MPa to 50MPa. This allows further reliably restraining stress damage in alight-receiving layer or a light-emitting/light-receiving layer duringformation of the second electrode.

Further, with the imaging element of the present disclosure, the imagingelement in the solid-state imaging device of the present disclosure, orthe electronic device of the present disclosure including theabove-described various preferable forms, surface roughness Ra of thesecond electrode preferably has a form of 1.5 nm or less and Rq of 2.5nm or less. Note that, the surface roughness Ra and Rq are based on aspecification in JIS B0601: 2013. Such smoothness of the secondelectrode can restrain surface diffuse reflectance in the secondelectrode and reduce surface reflection of the light entering the secondelectrode. This ensures restraining a loss of an amount of light of thelight entering the light-receiving layer or thelight-emitting/light-receiving layer via the second electrode andachieving an improvement in a light current characteristic inphotoelectric conversion.

Further, with the imaging element of the present disclosure, the imagingelement in the solid-state imaging device of the present disclosure, orthe electronic device of the present disclosure including theabove-described various preferable forms, a work function of the secondelectrode preferably has a form of 4.5 eV or less. Then, in this case, avalue of the work function of the second electrode is further preferableto be 4.1 eV to 4.5 eV.

Further, with the imaging element of the present disclosure, the imagingelement in the solid-state imaging device of the present disclosure, orthe electronic device of the present disclosure including theabove-described various preferable forms, optical transmittance of thesecond electrode with respect to light with wavelength of 400 nm to 660nm is preferably 75% or more. Additionally, the optical transmittance ofthe first electrode with respect to light with wavelength of 400 nm to660 nm is also preferably 75% or more.

Further, with the imaging element of the present disclosure, the imagingelement in the solid-state imaging device of the present disclosure, orthe electronic device of the present disclosure including theabove-described various preferable forms, an electric resistance valueof the second electrode is preferably 1×10⁻⁶Ω·cm or less. Alternatively,a sheet resistance value of the second electrode is preferably 3×10Ω/□to 1×10³Ω/□.

Further, with the imaging element of the present disclosure, the imagingelement in the solid-state imaging device of the present disclosure, orthe electronic device of the present disclosure including theabove-described various preferable forms, a thickness of the secondelectrode is 1×10⁻⁸ m to 1.5×10⁻⁷ m and preferably 2×10⁻⁸ m to 1×10⁻⁷ m.

Further, with the imaging element of the present disclosure, the imagingelement in the solid-state imaging device of the present disclosure, orthe electronic device of the present disclosure including theabove-described various preferable forms, the second electrode can havea constitution made of a material formed by adding or doping at leastone kind of material selected from the group consisting of aluminum,gallium, tin, and indium to one kind of material selected from the groupconsisting of indium oxide, tin oxide, and zinc oxide.

Alternatively, with the imaging element of the present disclosure, theimaging element in the solid-state imaging device of the presentdisclosure, or the electronic device of the present disclosure includingthe above-described various preferable forms, the second electrode canhave a constitution made of In_(a) (Ga, Al)_(b)Zn_(c)O_(d), that is,amorphous oxide constituted of quaternary compound at least constitutedof indium (In), gallium (Ga) and/or aluminum (Al), zinc (Zn), and oxygen(O). Then, in this case, a difference between the value of the workfunction of the second electrode and a value of the work function of thefirst electrode is preferable to be 0.4 eV or more. Further, setting thedifference between the value of the work function of the secondelectrode and the value of the work function of the first electrode tobe 0.4 eV or more, when a bias voltage is applied between the secondelectrode and the first electrode, generates an internal electric fieldin the light-receiving layer or the light-emitting/light-receiving layer(hereinafter, these layers may be collectively referred to as a“light-receiving layer or the like”) on the basis of the difference invalue of the work function and ensures a configuration that improvesinternal quantum efficiency, ensuring further restraining generation ofa dark current. Here, controlling an amount of introduced oxygen gas (anoxygen gas partial pressure) to form the second electrode by asputtering method can achieve controlling the value of the work functionof the second electrode.

Additionally, in the case where the second electrode has a constitutionmade of In_(a)(Ga, Al)_(b)Zn_(c)O_(d), the second electrode can also beconfigured to have a laminated structure of a second B layer and asecond A layer from a light-receiving layer or the like side, and avalue of the work function of the second A layer in the second electrodecan be lower than a value of the work function of the second B layer inthe second electrode. Then, in this case, the difference between thevalue of the work function of the second A layer in the second electrodeand the value of the work function of the second B layer in the secondelectrode can be configured to be 0.1 eV to 0.2 eV. Further, thedifference between the value of the work function of the first electrodeand the value of the work function of the second A layer in the secondelectrode can be configured to be 0.4 eV or more. Alternatively, settingthe difference between the value of the work function of the firstelectrode and the value of the work function of the second A layer inthe second electrode to 0.4 eV or more generates the internal electricfield in the light-receiving layer or the like on the basis of thedifference in the values of the work functions, allowing a configurationof achieving the improvement in internal quantum efficiency. Here, suchcontrol of the values of the work functions of the second A layer andthe second B layer in the second electrode can be achieved bycontrolling the amount of introduced oxygen gas (the oxygen gas partialpressure) at formation by the sputtering method. Besides, aconfiguration where a thickness of the second electrode is 1×10⁻⁸ m to1.5×10⁻⁷ m and a ratio of a thickness of the second A layer in thesecond electrode to a thickness of the second B layer in the secondelectrode is 9/1 to 1/9 can be employed. Note that, to reduce aninfluence of oxygen atoms and oxygen molecules to the light-receivinglayer or the like, configuring the thickness of the second B layerthinner than the thickness of the second A layer in the second electrodeis more preferable. Thus, the second electrode has a two-layer structureof the second A layer and the second B layer and the difference in thework function between the second B layer and the second A layer isspecified. This ensures achieving an optimization of the work functionin the second electrode, further easing an exchange (a movement) ofcarriers.

The electronic device of the present disclosure can constitute anoptical sensor and an image sensor. Then, in this case, thelight-emitting/light-receiving layer can be made of, for example, anorganic photoelectric conversion material.

With the imaging element of the present disclosure, the imaging elementin the solid-state imaging device of the present disclosure, or theelectronic device of the present disclosure including theabove-described various preferable forms and configurations (hereinafterthese devices are collectively referred to as an “imaging element or thelike of the present disclosure”), the light reception or the lightemission/light reception of the light (in a larger sense, anelectromagnetic wave including visible light, ultraviolet rays, andinfrared) on the imaging element or the like is performed via the secondelectrode.

The imaging element or the like of the present disclosure can employ aform where the second electrode is made of a transparent conductivematerial, specifically, indium-gallium oxide (IGO), indium-dopedgallium-zinc oxide (IGZO, In—GaZnO₄), aluminum oxide-doped zinc oxide(AZO), indium-zinc oxide (IZO), gallium-doped zinc oxide (GZO), and thelike. The value of the work function of the second electrode made ofthese transparent conductive materials is, for example, 4.1 eV to 4.5eV. Further, the imaging element or the like of the present disclosureincluding these forms can employ a form where the first electrode ismade of the transparent conductive material such as indium-tin oxide(ITO), indium-zinc oxide (IZO), and tin oxide (SnO₂). The value of thework function of the first electrode made of these transparentconductive materials is, for example, 4.8 eV to 5.0 eV.

As described above, with the imaging element or the like of the presentdisclosure, controlling the amount of introduced oxygen gas (the oxygengas partial pressure) to form the second electrode by the sputteringmethod can control the value of the work function of the secondelectrode. Additionally, controlling the amount of introduced oxygen gas(the oxygen gas partial pressure) to form the second electrode by thesputtering method can control the values of the work functions of thesecond A layer and the second B layer in the second electrode. Further,the imaging element or the like of the present disclosure can employ aform where a content rate of oxygen in the second electrode is less thana content rate of oxygen in a stoichiometric composition. Here, thevalue of the work function of the second electrode can be controlled onthe basis of the content rate of oxygen. As the content rate of oxygendecreases more than the content rate of oxygen in the stoichiometriccomposition, that is, as an oxygen loss increases, the value of the workfunction decreases. Note that, the content rate of oxygen of the secondA layer in the second electrode is lower than the content rate of oxygenof the second B layer in the second electrode.

The second electrode is formed by the sputtering method, specifically, amagnetron sputtering method and a parallel standard sheet sputteringmethod are applicable, and a plasma-generating formation method using aDC discharge method or an RF discharge method is applicable. Note that,the present disclosure has a major feature that the work function can becontrolled by oxygen flow rate (the amount of introduced oxygen gas andthe oxygen gas partial pressure).

As a method for forming the first electrode, although depending on thematerial constituting the first electrode, a PVD method such as a vacuumdeposition method, a reactive deposition method, various sputteringmethods, an electron beam evaporation method, and an ion plating method,various CVD methods including a pyrosol method, a method to thermallydissolve organic metal compounds, a spray method, a dip method, and aMOCVD method, an electroless plating method, and an electrolytic platingmethod are applicable.

To the electronic device of the present disclosure including theabove-described various preferable forms and configurations,specifically, for example, a configuration where the first electrode isformed on a substrate, the light-receiving layer or the like is formedon the first electrode, and the second electrode is formed on thelight-receiving layer or the like is applicable. That is, the electronicdevice of the present disclosure has a two-terminal type electronicdevice structure that includes the first electrode and the secondelectrode. However, the configuration is not limited to this. Theelectronic device may have a three-terminal type electronic devicestructure that further includes a control electrode. This makes itpossible to modulate a flowing current by an application of a voltage tothe control electrode. As three-terminal type electronic devicestructure, specifically, one with configuration and structure identicalto so-called bottom gate/bottom contact type, bottom gate/top contacttype, top gate/bottom contact type, or top gate/top contact typefield-effect type transistor (FET) is applicable. Note that, while thesecond electrode can be functioned as a cathode electrode (cathode)(that is, functioned as an electrode that extracts the electrons), thefirst electrode can be functioned as an anode electrode (anode) (thatis, functioned as an electrode that extracts holes). A structure wherethe light-receiving layer or the like is formed by lamination of aplurality of imaging elements and electronic devices that have differentoptical absorption spectra can also be employed. Besides, for example, astructure where the substrate is constituted of a silicon semiconductorsubstrate, driving circuits for the imaging elements and the electronicdevices and the light-receiving layers or the like are disposed on thissilicon semiconductor substrate, and the imaging elements and theelectronic devices are laminated on this silicon semiconductor substratecan also be employed.

The light-receiving layer or the like may be in an amorphous state ormay be a crystal state. As the organic material (the organicphotoelectric conversion material) constituting the light-receivinglayer or the like, an organic semiconductor material, an organic metalcompound, and organic semiconductor microparticles are applicable.Alternatively, as the material constituting the light-receiving layer orthe like, a metal oxide semiconductor, inorganic semiconductormicroparticles, a material whose core member is coated with a shellmember, and an organic-inorganic hybrid compound are also applicable.

Here, as the organic semiconductor material, specifically, an organicdye typified by quinacridone and its derivative, a dye formed bychelating an early period (indicates metal on the left in a periodictable) ion typified by Alq3[tris(8-quinolinolato) aluminum (III)] withan organic material, an organometallic dye complexly formed withtransition metal ion typified by phthalocyanine zinc (II) and an organicmaterial, dinaphthothienothiophene (DNTT), and the like are applicable.

As the organic metal compound, specifically, a dye formed by chelatingthe above-described early period ion with organic material and anorganic metal dye formed by complex formation with the transition metalion and the organic material are applicable. As the organicsemiconductor microparticles, specifically, an aggregate of the organicdye typified by the above-described quinacridone and its derivative, anaggregate of the dye formed by chelating the early period ion with theorganic material, an aggregate of the organic metal dye formed bycomplex formation with the transition metal ion and the organicmaterial, or prussian blue formed by crosslinking of metal ion withcyano group and its derivative, or a composite aggregate of thesematerials is applicable.

As the metal oxide semiconductor or the inorganic semiconductormicroparticles, specifically, ITO, IGZO, ZnO, IZO, IrO₂, TiO₂, SnO₂,SiO_(x), metal chalcogen semiconductor containing chalcogen [forexample, sulfur (S), selenium (Se), and tellurium (Te)] (specifically,CdS, CdSe, ZnS, CdSe/CdS, CdSe/ZnS, and PbSe), ZnO, CdTe, GaAs, and Siare applicable.

The material whose core member is coated with the shell member, that is,as a combination of (the core member and the shell member),specifically, an organic material such as (polystyrene and polyaniline)and a metallic material such as (a metallic material difficult to beionized and a metallic material easily ionized) are applicable. As theorganic-inorganic hybrid compound, specifically, the prussian blueformed by crosslinking of the metal ion with the cyano group and itsderivative are applicable. Besides, a coordination polymer, a genericterm for one formed by infinite crosslinking of metal ion withbipyridines, one formed by crosslinking of metal ion with multivalention acid typified by oxalic acid and rubeanic acid are applicable.

As a method for forming the light-receiving layer or the like, althoughdepending on the used material, an application method, a physical vapordeposition method (the PVD method); and various chemical vapordeposition methods (the CVD methods) including an MOCVD method areapplicable. Here, as the application method, specifically, a spin coatmethod; a soaking method; a cast method; various printing methods suchas a screen-printing method, an inkjet printing method, an offsetprinting method, and a gravure printing method; a stamping method; aspray method; and various coating methods such as an air doctor coatermethod, a blade coater method, a rod coater method, a knife coatermethod, a squeeze coater method, a reverse roll coater method, atransfer roll coater method, a gravure coater method, a kiss coatermethod, a cast coater method, a spray coater method, a slit orificecoater method, and a calendar coater method can be exemplified. Notethat, in the application method, as a solvent, nonpolar or low-polarityorganic solvent such as toluene, chloroform, hexane, and ethanol can beexemplified. Additionally, as the PVD method, an electron beam heatingmethod, a resistance heating method, and various vacuum depositionmethods such as a flash evaporation; a plasma deposition method; varioussputtering methods such as a two-pole sputtering method, a DC sputteringmethod, a DC magnetron sputtering method, a high frequency sputteringmethod, a magnetron sputtering method, an ion beam sputtering method,and a bias sputtering method; and various ion plating methods such as adirect current (DC) method, an RF method, a multi-cathode method, anactivation reaction method, an electric field deposition method, a highfrequency ion plating method, and a reactive ion plating method areapplicable.

Although the thickness of the light-receiving layer or the like is notlimited, for example, 1×10⁻¹⁰ m to 5×10⁻⁷ m can be exemplified.

As the substrate, an organic polymer exemplified bypolymethylmethacrylate (polymethylmethacrylate, PMMA), polyvinyl alcohol(PVA), polyvinylphenol (PVP), polyethersulfone (PES), polyimide,polycarbonate (PC), polyethylene terephthalate (PET), and polyethylenenaphthalate (PEN) (has a form of high-polymer material such as flexibleplastic film, plastic sheet, and plastic substrate made of high-polymermaterial) are applicable. The use of the substrate made of such flexiblehigh-polymer materials ensures an installation or integration of theelectronic device to, for example, an electronic appliance with curvedsurface shape. Alternatively, as the substrate, various glasssubstrates, various glass substrates that form an insulating film on asurface thereof, a quartz substrate, a quartz substrate that forms aninsulating film on a surface thereof, a silicon semiconductor substrate,a silicon semiconductor substrate that forms an insulating film on asurface thereof, and a metal substrate made of various alloys such asstainless steel and various metals are applicable. Note that, as theinsulating film, a silicon oxide-based material (for example, SiO_(x)and spin-on glass (SOG)); silicon nitride (SiN_(Y)); silicon oxynitride(SiON); aluminum oxide (Al₂O₃); metal oxide, and metal salt areapplicable. Additionally, a conductive substrate that forms theseinsulating films on the surface thereof (a substrate made of metal suchas gold and aluminum and a substrate made of highly oriented graphite)is also applicable. The surface of the substrate is preferably smooth;however, roughness to the extent that does not adversely affect thecharacteristic of the light-receiving layer or the like is acceptable.Adhesiveness between the first electrode and the substrate may beimproved by forming a silanol derivative on the surface of the substrateby silane coupling method, forming a thin film made of a thiolderivative, a carboxylic acid derivative, a phosphoric acid derivative,and the like by a SAM method or the like, and forming a thin film madeof insulating metal salt and metal complex by the CVD method or thelike.

Depending on the case, a coating layer may coat the second electrode andthe first electrode. As the material constituting the coating layer, notonly an inorganic insulating material exemplified by a siliconoxide-based material; silicon nitride (SiN_(Y)); and a metal oxidehigh-dielectric insulating film such as aluminum oxide (Al₂O₃), but alsoan organic insulating material (organic polymer) exemplified bystraight-chain hydrocarbons having on one end a functional group thatcan be bonded to a control electrode such as polymethylmethacrylate(PMMA); polyvinylphenol (PVP); polyvinyl alcohol (PVA); polyimide;polycarbonate (PC); polyethylene terephthalate (PET); polystyrene; asilanol derivative (a silane coupling agent) such asN-2(aminoethyl)3-aminopropyltrimethoxysilane (AEAPTMS),3-mercaptopropyltrimethoxysilane (MPTMS), or octadecyltrichlorosilane(OTS); octadecanethiol, and dodecyl isocyanate are applicable. Acombination of these can also be used. Note that, as the siliconoxide-based material, silicon oxide (SiO_(x)), BPSG, PSG, BSG, AsSG,PbSG, silicon oxynitride (SiON), SOG (spin-on glass), or alow-dielectric constant material (for example, polyarylether,cycloperfluorocarbon polymer and benzocyclobutene, a cyclic fluororesin,polytetrafluoroethylene, fluorinatedaryl ether, fluorinated polyimide,amorphous carbon, and organic SOG) can be exemplified. As the method forforming the insulating layer, any one of the above-described various PVDmethods; various CVD methods; a spin coat method; the above-describedvarious application methods; a sol-gel method; an electrodepositionmethod; a shadow mask method; and a spray method is applicable.

First Embodiment

The first embodiment relates to the imaging element of the presentdisclosure and the electronic device of the present disclosure. FIG. 1Billustrates a schematic, partial cross-sectional view of the imagingelement or the electronic device of the first embodiment.

The imaging element and the electronic device of the first embodiment oran imaging element and an electronic device of a second embodiment,which will be described later, have a laminated structure including afirst electrode 21, a light-receiving layer or alight-emitting/light-receiving layer (a light-receiving layer or thelike 23) formed on the first electrode 21, and a second electrode 22,which is formed on the light-receiving layer or the like 23. Then, thesecond electrode 22 is made of a transparent amorphous oxide havingconductive property. Here, the second electrode 22 is made of a materialformed by adding or doping at least one kind of material selected fromthe group consisting of aluminum, gallium, tin, and indium to one kindof material selected from the group consisting of indium oxide, tinoxide, and zinc oxide. Alternatively, the second electrode 22 is made ofIn_(a)(Ga, Al)_(b)Zn_(c)O_(d). That is, the second electrode 22 is madeof the amorphous oxide at least constituted of quaternary compound[In_(a)(Ga, Al)_(b)Zn_(c)O_(d)] of indium (In), gallium (Ga) and/oraluminum (Al), zinc (Zn), and oxygen (O). Note that, “a,” “b,” “c,” and“d” can be various values. Note that, 0.5 to 1 can be an example as thevalue of “a,” 0.5 to 1 as the value of “b,” 0.5 to 1 as the value of“c,” and 4 to 7 as the value of “d”; however, values are not limited tothese.

Here, more specifically, the imaging element and the electronic deviceof the first embodiment include the first electrode 21 formed on asubstrate 10 formed of the silicon semiconductor substrate, thelight-receiving layer or the like 23 formed on the first electrode 21,and the second electrode 22 formed on the light-receiving layer or thelike 23. That is, the electronic device of the first embodiment or thesecond embodiment, which will be described later, has a two-terminaltype electronic device structure that includes the first electrode 21and the second electrode 22. Specifically, the light-receiving layer orthe like 23 performs a photoelectric conversion. Then, in the electronicdevice of the first embodiment or the second embodiment, which will bedescribed later, a difference between a value of the work function ofthe second electrode 22 and a value of the work function of the firstelectrode 21 is 0.4 eV or more. Here, setting the difference between thevalue of the work function of the second electrode 22 and the value ofthe work function of the first electrode 21 to 0.4 eV or more generatesan internal electric field on the light-receiving layer or the like 23on the basis of the difference in the values of the work functions, thusachieving improvement in internal quantum efficiency. The secondelectrode 22 functions as a cathode electrode (cathode). That is, thesecond electrode 22 functions as an electrode to extract electrons. Onthe other hand, the first electrode 21 functions as an anode electrode(anode). That is, the first electrode 21 functions as an electrode toextract holes. The light-receiving layer or the like 23 is made of anorganic photoelectric conversion material, specifically, for example,quinacridone with thickness of 0.1 μm.

Further, the work function of the second electrode 22 is 4.5 eV or less,specifically, 4.1 eV to 4.5 eV. More specifically, in the firstembodiment, the second electrode 22 is made of a transparent conductivematerial such as indium-zinc oxide (IZO) or indium-doped gallium-zincoxide (IGZO). Additionally, the first electrode 21 is made of atransparent conductive material such as indium-tin oxide (ITO). Here,although depending on a film forming condition, a work function of IZOor IGZO is 4.1 eV to 4.3 eV. Further, although depending on a filmforming condition, a work function of ITO is 4.8 eV to 5.0 eV. Notethat, besides, as the material constituting the second electrode 22, atransparent conductive material such as aluminum oxide-doped zinc oxide(AZO), indium-gallium oxide (IGO) or gallium-doped zinc oxide (GZO) isapplicable. Besides, as the material constituting the first electrode21, a transparent conductive material such as indium-zinc oxide (IZO)and tin oxide (SnO₂) formed with a film forming condition different fromthe second electrode 22 is applicable. Note that, the above-describedexplanation is almost similar to the second embodiment, which will bedescribed later.

Then, with the imaging element and the electronic device of the firstembodiment or the second embodiment, which will be described later,optical transmittance of the second electrode 22 with respect to lightwith wavelength of 400 nm to 660 nm is 75% or more. Opticaltransmittance of the first electrode 21 with respect to the light withwavelength of 400 nm to 660 nm is also 75% or more. Forming films of thesecond electrode 22 and the first electrode 21 on a transparent glassplate ensures the measurement of the optical transmittance of the secondelectrode 22 and the first electrode 21. Additionally, an electricresistance value of the second electrode 22 is 1×10⁻⁶Ω·cm or less, and asheet resistance value of the second electrode 22 is 3×10Ω/□ to1×10³Ω/□. A thickness of the second electrode 22 is 1×10⁻⁸ m to 1.5×10⁻⁷m and preferably 2×10⁻⁸ m to 1×10⁻⁷ m. Further, surface roughness Ra ofthe second electrode 22 is 1.5 nm or less and Rq is 2.5 nm or less. Morespecifically, the electric resistance value of the second electrode 22made of IZO with thickness of 100 μm is 6×10⁻⁶Ω·cm, and the sheetresistance value is 60Ω/□. Additionally, the electric resistance valueof the second electrode 22 made of IGZO with thickness of 100 μm is2×10⁻⁵Ω·cm, and the sheet resistance value is 2×10²Ω/□.

The following describes a method for manufacturing the imaging elementand the electronic device of the first embodiment with reference to FIG.1A and FIG. 1B.

[Process-100]

The substrate 10 formed of the silicon semiconductor substrate isprepared. Here, the substrate 10 includes, for example, a drivingcircuit for the imaging element and the electronic device, thelight-receiving layer or the like (these members are not illustrated),and a wiring 11, and an insulating layer 12 is formed on a surfacethereof. The insulating layer 12 has an opening 13 on a bottom portionthereof where the wiring 11 is exposed. Then, the first electrode 21made of ITO is formed (film formation) over the insulating layer 12including the inside of the opening 13 by the sputtering method (seeFIG. 1A).

[Process-110]

Next, after performing patterning of the first electrode 21, thelight-receiving layer or the like 23 made of quinacridone is formed(film formation) over an entire surface of the first electrode 21 byvacuum deposition method. Further, the second electrode 22 made of IZOor IGZO is formed (film formation) over the light-receiving layer or thelike 23 by the sputtering method. Thus, the electronic device of thefirst embodiment with the structure illustrated in FIG. 1B can beobtained.

Here, controlling the amount of introduced oxygen gas (the oxygen gaspartial pressure) to form the second electrode 22 by the sputteringmethod controls the value of the work function of the second electrode22. FIG. 2 illustrates the graph of an example of results obtaining arelationship between the oxygen gas partial pressure and the value ofthe work function of the second electrode 22 made of IGZO. As a value ofthe oxygen gas partial pressure increases, that is, as oxygen lossdecreases, the value of the work function of the second electrode 22increases. As the value of the oxygen gas partial pressure decreases,that is, as the oxygen loss increases, the value of the work function ofthe second electrode 22 decreases. Note that, as a sputtering device, aparallel standard sheet sputtering device or a DC magnetron sputteringdevice was employed, argon (Ar) gas was used as process gas, and anInGaZnO₄ sintered body was used as a target. Note that, a relationshipbetween the oxygen gas partial pressure and the value of the workfunction of the second electrode 22 made of IZO also has a relationshipsimilar to the relationship between the oxygen gas partial pressure andthe value of the work function of the second electrode 22 made of IGZO.

Thus, with the electronic device of the first embodiment, controllingthe amount of introduced oxygen gas (the oxygen gas partial pressure) toform the second electrode 22 by the sputtering method controls the valueof the work function of the second electrode 22. Note that, in thesecond electrode 22, a content rate of oxygen is less than the contentrate of oxygen in the stoichiometric composition.

FIG. 3A and FIG. 3B illustrate an I-V curve obtained from the imagingelement and the electronic device (the photoelectric conversion element)of the first embodiment, which includes the second electrode 22 made ofIZO, and an imaging element and an electronic device (a photoelectricconversion element) of a first comparative example. Note that, FIG. 3Aillustrates a light current while FIG. 3B illustrates a dark current.Additionally, “A” in FIG. 3A and FIG. 3B indicates measurement resultsof the imaging element and the electronic device of the firstembodiment, and “B” indicates measurement results of the imaging elementand the electronic device of the first comparative example. Here, theelectronic device of the first comparative example is constituted of thesecond electrode 22 in the electronic device of the first embodimentmade of ITO instead of IZO. Besides, the imaging element and theelectronic device of the first embodiment described below include thesecond electrode 22 made of IZO.

From FIG. 3B, the imaging element and the electronic device of the firstembodiment hardly change up to a reverse-bias voltage of −5 bolts (FIG.3B illustrates the reverse-bias voltage up to −3 bolts). That is, when 0bolts are applied between the first electrode 21 and the secondelectrode 22, a value of the dark current flowing between the firstelectrode 21 and the second electrode 22 is assumed as J_(d-0) (ampere),and when 5 bolts are applied (when the reverse-bias voltage of −5 boltsare applied) between the first electrode 21 and the second electrode 22,the value of the dark current flowing between the first electrode 21 andthe second electrode 22 is assumed as J_(d-5) (ampere). Then,0.8≦J_(d-5)/J_(d-0)≦1.2 is met. Additionally, when a voltage exceeding 0bolts to 5 bolts or less (the reverse-bias voltage) is applied betweenthe first electrode 21 and the second electrode 22, the value of thedark current flowing between the first electrode 21 and the secondelectrode 22 is assumed as J_(d)(ampere), 0.8≦J_(d)/J_(d-0)≦1.2 is met.

Additionally, values of the internal quantum efficiency of theelectronic devices of the first embodiment and first comparative exampleand values of an on/off ratio were as shown in the following Table 1.Note that, an internal quantum efficiency η is a ratio of the number ofgenerated electrons with respect to the number of incident photons andcan be expressed by the following formula.

η={(h·c)/(q·λ)}(I/P)=(1.24/λ)(I/P)

Here,

h: Planck's constantc: velocity of lightq: electric charge of electronA: wavelength of incident light (μm)I: light current and a current value obtained at the reverse-biasvoltage of 1 bolt at the measurement in the first embodiment(ampere/cm²)P: power of incident light (ampere/cm²)

Further, Table 2 shows measurement results of the surface roughness Raand Rq and measurement results of the optical transmittance of thesecond electrodes 22 of the first embodiment and the first comparativeexample.

TABLE 1 Internal quantum efficiency On/off ratio First embodiment 63 3.4First comparative example 45 1.6

TABLE 2 First comparative First embodiment example Ra 0.36 nm 2.5 nm Rq0.46 nm 3.6 nm Optical transmittance with 93% 78% wavelength of 450 nmOptical transmittance with 88% 84% wavelength of 550 nm

Since the electronic device of the first comparative example includesthe second electrode and the first electrode both made of ITO, as FIG.4B illustrates a conceptual diagram of energy diagram, there is nodifference between the value of the work function of the first electrodeand the value of the work function of the second electrode. Therefore,the holes from the first electrode easily flow into the secondelectrode, and consequently, the dark current increases. Additionally,since there is no difference between the value of the work function ofthe first electrode and the value of the work function of the secondelectrode, when the electrons and the holes are extracted, a potentialgradient is absent (that is, the internal electric field does not occurin the light-receiving layer or the like). This makes it difficult tosmoothly extract the electrons and the holes (see the conceptual diagramin FIG. 4D). On the other hand, the electronic device of the firstembodiment includes the second electrode made of IZO and the firstelectrode made of ITO. The difference between the value of the workfunction of the first electrode and the value of the work function ofthe second electrode is 0.4 eV or more. FIG. 4A illustrates theconceptual diagram of the energy diagram. Therefore, as a result ofensuring a prevention of the holes from the first electrode flowing intothe second electrode, the generation of the dark current can berestrained. Additionally, since the difference between the value of thework function of the first electrode and the value of the work functionof the second electrode is 0.4 eV or more, the potential gradient isgenerated at the extraction of the electrons and the holes (that is, theinternal electric field occurs in the light-receiving layer or thelike). This ensures the smooth extraction of the electrons and the holesapplying this potential gradient (see the conceptual diagram in FIG. 4C)

Additionally, the relationship between the oxygen gas partial pressureand the internal stress of the laminated structure during the filmformation of the second electrode 22 was examined. As a sputteringdevice, the parallel corrugated sheet sputtering device or the DCmagnetron sputtering device was employed, argon (Ar) gas was used asprocess gas, and an InZnO sintered body was used as a target. FIG. 5illustrates the result. Here, the horizontal axis in FIG. 5 indicatesthe oxygen gas partial pressure<=(O₂ gas pressure)/(sum of Ar gas and O₂gas pressures)>, and the vertical axis indicates the internal stress ofthe laminated structure (unit: MPa). Additionally, the data illustratedin FIG. 5 is data of the laminated structure obtained by forming thefirst electrode made of ITO with thickness of 100 nm, thelight-receiving layer or the like made of quinacridone with thickness of100 nm, and the second electrode (the first embodiment) made of IZO,amorphous oxide, with thickness of 100 nm or the second electrode (thefirst comparative example) made of ITO, crystal oxide, with thickness of100 nm on a glass substrate in this order. Note that, the IZO film orthe ITO film was formed at room temperature (specifically, 22° C. to 28°C.) by the sputtering method. Further, the laminated structure wasformed on a silicon wafer. The internal stress was measured by awell-known method using a commercially available thin film stressmeasuring device.

Further, the obtained second electrode was provided for X-raydiffraction test. FIG. 6A and FIG. 6B illustrate the results. Note that,FIG. 6A is a chart illustrating the X-ray diffraction analysis resultsof the second electrode of the first comparative example. FIG. 6B is achart illustrating the X-ray diffraction analysis results of the secondelectrode of the first embodiment. It is found from FIG. 6B that, thesecond electrode of the first embodiment is amorphism regardless of thefilm forming condition. Additionally, it is found from FIG. 6A that, thesecond electrode of the first comparative example has high crystalline.Note that, “a,” “b,” “c,” and “d” for the charts in FIG. 6B indicate adifference in film forming condition. The chart “a” indicates data witha sputtering input electric power of 200 watts. The chart “b” indicatesdata with the sputtering applying electric power of 150 watts. The chart“c” indicates data with the sputtering applying electric power of 100watts. The chart “d” indicates data with the sputtering applyingelectric power of 50 watts.

Additionally, it is found from FIG. 5 that, with the imaging element andthe electronic device of the first embodiment, the laminated structurehas the internal stress with the compressive stress of 10 MPa to 50 MPa.On the other hand, with the imaging element and the electronic device ofthe first comparative example, it is found that the laminated structurehas the internal stress with considerably high compressive stress, 150MPa to 180 MPa. Respective samples of the laminated structures formed onthe silicon wafer to measure the stress were dipped in acetone for 30seconds. After that, using an optical microscope (scaling factor: 5powers), a state of insulating layers was observed. Consequently, thefirst embodiment had no change before and after the dipping. Meanwhile,in the first comparative example, a peeling was partially recognizedbetween the light-receiving layer or the like and the second electrode.Thus, the test has found that, constituting the second electrode 22 byamorphous oxide allows reliably restraining the stress damage in thelight-receiving layer or the like during the formation of the secondelectrode 22.

Next, the second electrode of the first embodiment was examined forsealing property. Specifically, the second electrode was evaluated forpermeability. For the evaluation on permeability, specifically, a LowTemperature Oxide (LTO, a low temperature CVD-SiO₂) film with thicknessof 0.1 μm was formed on a silicon semiconductor substrate. A transparentconductive material constituting the second electrode was formed on thisLTO film. Then, being left under the atmosphere, an amount of warp,which occurs and changes over time by absorbing water vapor inatmosphere by the LTO film via the transparent conductive material, ofthe laminated structures formed of the silicon semiconductor substrate,the LTO film, and the transparent conductive material was measured.

FIG. 9A illustrates measurement results the amount of warp in the ITOfilm and the IZO films with different internal stress. Here, in FIG. 9A,“A” indicates the measurement result of the IZO film with internalstress of −10 MPa (the compressive stress: 10 MPa), “B” indicates themeasurement result of the IZO film with internal stress of −50 MPa (thecompressive stress: 50 MPa), and “C” indicates the measurement result ofthe ITO film with internal stress of −250 MPa (the compressive stress:250 MPa). It is found that, compared with the ITO film, the IZO film hasthe high sealing property (the low permeability).

The imaging elements that include the second electrode (the imagingelement of the first embodiment and the imaging element of the firstcomparative example) were prototyped from the respective IZO film withinternal stress of −250 MPa and ITO film with internal stress of −50MPa. FIG. 9B illustrates results of taking images of imaging devicesconstituted of these imaging elements. FIG. 9B also illustrates scanningelectron micrographs of surfaces of the IZO film and the ITO film. FromFIG. 9B, it is apparent that the result of image-taking of the imagingelement of the first embodiment, which includes the second electrodeconstituted of the IZO film, substantially improves unevenness insensitivity compared with the result of image-taking of the imagingelement of the first comparative example that includes the secondelectrode constituted of the ITO film. It is considered that theimprovement in sealing property (the deterioration in permeability)owing to the amorphous IZO film substantially contributes to thereduction in unevenness in sensitivity. Besides, it is considered that,from the scanning electron micrographs of the surfaces, since the ITOfilm has the crystalline, the water vapor is likely to enter easily.Meanwhile, the IZO film is amorphous and therefore is uniform, therebyrestraining the entrance of the water vapor.

The case where the second electrode 22 is made of IGZO instead of IZOalso obtained the result similar to the above-described result.

As described above, since the imaging element and the electronic deviceof the first embodiment include the transparent second electrode withconductive property, the incident light can reliably reach thelight-receiving layer or the like. Moreover, since the second electrodeis made of the amorphous oxide, the internal stress decreases at thesecond electrode. Accordingly, even without forming a stress bufferlayer, which has complex configuration and structure, the stress damageis less likely to occur in the light-receiving layer or the like duringthe formation of the second electrode. Moreover, with the imagingelement and the electronic device of the first embodiment, since thedifference between the value of the work function of the first electrodeand the value of the work function of the second electrode is specified,when the bias voltage (more specifically, the reverse-bias voltage) isapplied between the second electrode and the first electrode, the largeinternal electric field can be generated in the light-receiving layer orthe like on the basis of the difference in the values of the workfunctions. As a result of this, the improvement can be achieved in theinternal quantum efficiency, that is, an increase in photo current canbe achieved, and also the dark current can be restrained. Besides, sincethe surface of the second electrode is considerably smooth, a surfacediffuse reflectance in the second electrode can be restrained. As aresult, a surface reflection of light entering the second electrode isreduced. This ensures restraining the loss of amount of light of thelight entering the light-receiving layer or the like via the secondelectrode, thereby ensuring further improving the light currentcharacteristic in the photoelectric conversion. Further, the secondelectrode of the first embodiment has the high sealing property and thelow permeability, thereby substantially improving the unevenness insensitivity of the imaging element and the electronic device of thefirst embodiment.

Second Embodiment

The second embodiment is a modification of the first embodiment. FIG. 1Cillustrates a schematic, partial cross-sectional view of the electronicdevice of the second embodiment.

The electronic device of the second embodiment includes the secondelectrode 22 having a laminated structure of a second B layer 22B and asecond A layer 22A from a light-receiving layer or the like side. Avalue of the work function of the second A layer 22A in the secondelectrode 22 is lower than a value of the work function of the second Blayer 22B in the second electrode 22. Specifically, a difference betweenthe value of the work function of the second A layer 22A in the secondelectrode 22 and the value of the work function of the second B layer22B in the second electrode 22 is 0.1 eV to 0.2 eV, more specifically,0.15 eV. A difference between the value of the work function of thefirst electrode 21 and the value of the work function of the second Alayer 22A in the second electrode 22 is 0.4 eV or more. Additionally,the thickness of the second electrode 22 is 1×10⁻⁸ m to 1.5×10⁻⁷ m,specifically, 50 nm, and the ratio of the thickness of the second Alayer 22A in the second electrode 22 to the thickness of the second Blayer 22B in the second electrode 22 is 9/1 to 1/9, specifically, 9/1.In the second embodiment as well, setting the difference between thevalue of the work function of the first electrode 21 and the value ofthe work function of the second A layer 22 in the second electrode 22 to0.4 eV or more generates the internal electric field on thelight-receiving layer or the like on the basis of the difference in thevalues of the work functions, thus achieving the improvement in internalquantum efficiency. Here, assume that a composition of the second Alayer 22A as In_(a) (Ga, Al)_(b)Zn_(c)O_(d) and a composition of thesecond B layer 22B as In_(a′) (Ga, Al)_(b′)Zn_(c′)O_(d′), a=a′, b=b′,and c=c′, and further d<d′ is met.

In a method for forming the electrode for the electronic device of thesecond embodiment, in a process similar to [Process-110] in the firstembodiment, for example, as illustrated in the graph in FIG. 2,controlling the amount of introduced oxygen gas during the formation bythe sputtering method controls the values of the work functions of thesecond A layer 22A and the second B layer 22B in the second electrode22.

With the electronic device of the second embodiment, the secondelectrode is constituted of the second A layer and the second B layerand further the difference between the work functions of the second Alayer and the second B layer is specified. This ensures achieving theoptimization of the work functions in the second electrode, furthereasing the exchange (the movement) of the carriers.

Third Embodiment

The third embodiment relates to a solid-state imaging device of thepresent disclosure. The solid-state imaging device of the thirdembodiment includes the plurality of imaging elements (the photoelectricconversion elements) of the first embodiment and the second embodiment.

FIG. 7 illustrates the conceptual diagram of the solid-state imagingdevice of the third embodiment, and FIG. 8 illustrates the configurationof the solid-state imaging device of the third embodiment. An imagingdevice 100 of the third embodiment is constituted of a solid-stateimaging device and well-known lens group 101, digital signal processor(DSP) 102, frame memory 103, display device 104, storage device 105,operating system 106, and power supply system 107. These members areelectrically connected with a bus line 108. Then, the solid-stateimaging device 40 of the third embodiment is constituted of an imagingarea 41 where the imaging elements described in the first embodiment andthe second embodiment are arranged in a two-dimensional array pattern onthe semiconductor substrate (for example, the silicon semiconductorsubstrate), a vertical driving circuit 42, column signal processingcircuits 43, a horizontal driving circuit 44, an output circuit 45, anda control circuit 46 as its peripheral circuits, and the like. Notethat, it is obvious that these circuits can be constituted of well-knowncircuits or can be constituted using another circuit configuration (forexample, various circuits used in conventional CCD imaging device andCMOS imaging device).

The control circuit 46 generates a clock signal and a control signalserving as a reference for operations of the vertical driving circuit42, the column signal processing circuits 43, and the horizontal drivingcircuit 44 on the basis of a vertical synchronization signal, ahorizontal synchronization signal, and a master clock. Then, thegenerated clock signal and control signal are input to the verticaldriving circuit 42, the column signal processing circuits 43, and thehorizontal driving circuit 44.

The vertical driving circuit 42 is, for example, constituted of a shiftregister and sequentially selects and scans the respective imagingelements 30 in the imaging area 41 in a vertical direction in units ofrows. Then, a pixel signal based on a current (a signal) generatedaccording to an amount of received light in each imaging element 30 istransmitted to the column signal processing circuit 43 via a verticalsignal line 47.

The column signal processing circuits 43 are, for example, disposed foreach column of the imaging elements 30. Noise removal and signalprocessing to amplify the signals are performed on signals output fromthe imaging elements 30 in one row by signals from black referencepixels (although not illustrated, the black reference pixels are formedat a peripheral area of a valid pixel area). At an output stage of thecolumn signal processing circuit 43, a horizontal selection switch (notillustrated) is disposed coupled between the column signal processingcircuit 43 and a horizontal signal line 48.

The horizontal driving circuit 44 is, for example, constituted of theshift register. Sequentially outputting horizontal scanning pulsessequentially selects each of the column signal processing circuits 43and outputs signals from the respective column signal processingcircuits 43 to the horizontal signal lines 48.

The output circuit 45 performs signal processing on signals sequentiallysupplied from the respective column signal processing circuits 43 viathe horizontal signal lines 48 and outputs the signals.

Although depending on the material constituting the light-receivinglayer or the like, since the light-receiving layer or the like itselfcan have a configuration functioning as a color filter. This ensuresseparating colors without disposing a color filter. However, dependingon the case, a well-known color filter to transmit a specific wavelengthsuch as red, green, blue, cyan, magenta, and yellow may be disposed atthe upper side of the imaging elements 30 on a light-incident side.Besides, the solid-state imaging device can be a front surfaceilluminated type and also can be a back surface illuminated type.Additionally, as necessary, a shutter to control the incident light tothe imaging element may be disposed.

This disclosure has been described above on the basis of the preferableembodiments; however, the present disclosure is not limited to theseembodiments. The structures, the configurations, the manufacturingconditions, the manufacturing methods, and the materials used for theimaging element, the electronic device, and the solid-state imagingdevice described in the embodiments are examples and can beappropriately changed. To cause the electronic device of the presentdisclosure to function as a solar cell, it is only necessary toirradiate the light-receiving layer or the like with light in a statewhere the voltage is not applied between the second electrode and thefirst electrode. Additionally, the optical sensor and the image sensorcan be configured with the electronic device of the present disclosure.

Note that, the following configurations are also applicable to thepresent disclosure.

[A01]<<Imaging Element>>

An imaging element including

a laminated structure including a first electrode, a light-receivinglayer formed on the first electrode, and a second electrode formed onthe light-receiving layer,

wherein the second electrode is made of a transparent amorphous oxidehaving a conductive property.

[A02] The imaging element according to [A01],

wherein assuming that a value of a dark current flowing between thefirst electrode and the second electrode is J_(d-0) (ampere) when 0bolts are applied between the first electrode and the second electrode,and assuming that a value of the dark current flowing between the firstelectrode and the second electrode is J_(d-5) (ampere) when 5 bolts areapplied between the first electrode and the second electrode,0.8≦J_(d-5)/J_(d-0)≦1.2 is met.

[A03] The imaging element according to [A01] or [A02], wherein thelaminated structure has an internal stress with compressive stress of 10MPa to 50 MPa.[A04] The imaging element according to any one of [A01] to [A03],wherein the second electrode has a surface roughness Ra of 1.5 nm orless and Rq of 2.5 nm or less.[A05] The imaging element according to any one of [A01] to [A04],wherein the second electrode has a work function of 4.5 eV or less.[A06] The imaging element according to [A05], wherein the secondelectrode has a value of the work function of 4.1 eV to 4.5 eV.[A07] The imaging element according to any one of [A01] to [A06],wherein the second electrode has an optical transmittance of 75% or morewith respect to light with wavelength of 400 nm to 660 nm.[A08] The imaging element according to any one of [A01] to [A07],wherein the second electrode has an electric resistance value of1×10⁻⁶Ω·cm or less.[A09] The imaging element according to any one of [A01] to [A08],wherein the sheet resistance value of the second electrode is 3×10Ω/□ to1×10³Ω/□.[A10] The imaging element according to any one of [A01] to [A09],wherein the second electrode has a thickness of 1×10⁻⁸ m to 1.5×10⁻⁷ m.[A11] The imaging element according to [A10], wherein the secondelectrode has the thickness of 2×10⁻⁸ m to 1×10⁻⁷ m.[A12] The imaging element according to any one of [A01] to [A11],wherein the second electrode is made of a material formed by adding ordoping at least one kind of material selected from the group consistingof aluminum, gallium, tin, and indium to one kind of material selectedfrom the group consisting of indium oxide, tin oxide, and zinc oxide.[A13] The imaging element according to any one of [A01] to [A11],wherein the second electrode is made of In_(a)(Ga, Al)_(b)Zn_(c)O_(d).[A14] The imaging element according to [A12] or [A13], wherein adifference between a value of a work function of the second electrodeand a value of the work function of the first electrode is 0.4 eV ormore.[A15] The imaging element according to [A14], wherein setting thedifference between the value of the work function of the secondelectrode and the value of the work function of the first electrode to0.4 eV or more generates an internal electric field in thelight-receiving layer on the basis of the difference in the values ofthe work functions and achieves improvement in internal quantumefficiency.[A16] The imaging element according to [A13],

wherein the second electrode has a laminated structure of a second Blayer and a second A layer from the light-receiving layer side, and

a value of a work function of the second A layer in the second electrodeis lower than a value of the work function of the second B layer in thesecond electrode.

[A17] The imaging element according to [A16], wherein a differencebetween the value of the work function of the second A layer in thesecond electrode and the value of the work function of the second Blayer in the second electrode is 0.1 eV to 0.2 eV.[A18] The imaging element according to [A16] or [A17], wherein adifference between a value of the work function of the first electrodeand the value of the work function of the second A layer in the secondelectrode is 0.4 eV or more.[A19] The imaging element according to [A18], wherein setting thedifference between the value of the work function of the first electrodeand the value of the work function of the second A layer in the secondelectrode to 0.4 eV or more generates an internal electric field in thelight-receiving layer on the basis of the difference in the values ofthe work functions and achieves improvement in internal quantumefficiency.[A20] The imaging element according to any one of [A16] to [A19],wherein the thickness of the second electrode is 1×10⁻⁸ m to 1.5×10⁻⁷ mand a ratio of a thickness of a second A layer of the second electrodeto a thickness of a second B layer of the second electrode is 9/1 to1/9.[A21] The imaging element according to any one of [A01] to [A20],wherein the second electrode is made of indium-gallium oxide,indium-doped gallium-zinc oxide, aluminum oxide-doped zinc oxide,indium-zinc oxide, or gallium-doped zinc oxide.[A22] The imaging element according to any one of [A01] to [A21],wherein the first electrode is made of indium-tin oxide, indium-zincoxide, or tin oxide.[A23] The imaging element according to any one of [A01] to [A22],wherein controlling an amount of introduced oxygen gas to form thesecond electrode by a sputtering method controls the value of the workfunction of the second electrode.[A24] The imaging element according to any one of [A01] to [A23],wherein a content rate of oxygen in the second electrode is less than acontent rate of oxygen in a stoichiometric composition.

[B01]<<Solid-state Imaging Device>>

A solid-state imaging device including a plurality of imaging elements,

wherein the imaging elements each have a laminated structure including afirst electrode, alight-receiving layer formed on the first electrode,and a second electrode formed on the light-receiving layer, and

the second electrode is made of a transparent amorphous oxide having aconductive property.

[B02] A solid-state imaging device includes the plurality of imagingelements according to any one of [A01] to [A24].[C01] An electronic device including

a laminated structure including a first electrode, alight-emitting/light-receiving layer formed on the first electrode, anda second electrode formed on the light-emitting/light-receiving layer,

wherein the second electrode is made of a transparent amorphous oxidehaving a conductive property.

[C02] The electronic device according to [C01], wherein assuming that avalue of a dark current flowing between the first electrode and thesecond electrode is J_(d-0) (ampere) when 0 bolts are applied betweenthe first electrode and the second electrode, and assuming that a valueof the dark current flowing between the first electrode and the secondelectrode is J_(d-5) (ampere) when 5 bolts are applied between the firstelectrode and the second electrode, 0.8≦J_(d-5)/J_(d-0)≦1.2 is met.[C03] The electronic device according to [C01] or [C02], wherein thelaminated structure has an internal stress with compressive stress of 10MPa to 50 MPa.[C04] The electronic device according to any one of [C01] to [C03],wherein the second electrode has a surface roughness Ra of 1.5 nm orless and Rq of 2.5 nm or less.[C05] The electronic device according to any one of [C01] to [C04],wherein the second electrode has a work function of 4.5 eV or less.[C06] The electronic device according to [C05], wherein the secondelectrode has a value of the work function of 4.1 eV to 4.5 eV.[C07] The electronic device according to any one of [C01] to [C06],wherein the second electrode has an optical transmittance of 75% or morewith respect to light with wavelength of 400 nm to 660 nm.[C08] The electronic device according to any one of [C01] to [C07],wherein the second electrode has an electric resistance value of1×10⁻⁶Ω·cm or less.[C09] The electronic device according to any one of [C01] to [C08],wherein the sheet resistance value of the second electrode is 3×10Ω/□ to1×10³Ω/□.[C10] The electronic device according to any one of [C01] to [C09],wherein the second electrode has a thickness of 1×10⁻⁸ m to 1.5×10⁻⁷ m.[C11] The electronic device according to [C10], wherein the secondelectrode has the thickness of 2×10⁻⁸ m to 1×10⁻⁷ m.[C12] The electronic device according to any one of [C01] to [C11],wherein the second electrode is made of a material formed by adding ordoping at least one kind of material selected from the group consistingof aluminum, gallium, tin, and indium to one kind of material selectedfrom the group consisting of indium oxide, tin oxide, and zinc oxide.[C13] The electronic device according to any one of [C01] to [C11],wherein the second electrode is made of In_(d)(Ga, Al)_(b)Zn_(c)O_(d).[C14] The electronic device according to [C12] or [C13], wherein adifference between a value of a work function of the second electrodeand a value of the work function of the first electrode is 0.4 eV ormore.[C15] The electronic device according to [C14], wherein setting thedifference between the value of the work function of the secondelectrode and the value of the work function of the first electrode to0.4 eV or more generates an internal electric field in thelight-receiving layer on the basis of the difference in the values ofthe work functions and achieves improvement in internal quantumefficiency.[C16] The electronic device according to [C13], wherein the secondelectrode has a laminated structure constituted of a second B layer anda second A layer from the light-emitting/light-receiving layer side. Avalue of the work function of the second A layer in the second electrodeis lower than a value of the work function of the second B layer in thesecond electrode.[C17] The electronic device according to [C16], wherein a differencebetween the value of the work function of the second A layer in thesecond electrode and the value of the work function of the second Blayer in the second electrode is 0.1 eV to 0.2 eV.[C18] The electronic device according to [C16] or [C17], wherein adifference between a value of the work function of the first electrodeand the value of the work function of the second A layer in the secondelectrode is 0.4 eV or more.[C19] The electronic device according to [C18], wherein setting thedifference between the value of the work function of the first electrodeand the value of the work function of the second A layer in the secondelectrode to 0.4 eV or more generates an internal electric field in thelight-emitting/light-receiving layer on the basis of the difference inthe values of the work functions and achieves improvement in internalquantum efficiency.[C20] The electronic device according to any one of [C16] to [C19],wherein the thickness of the second electrode is 1×10⁻⁸ m to 1.5×10⁻⁷ mand a ratio of a thickness of a second A layer of the second electrodeto a thickness of a second B layer of the second electrode is 9/1 to1/9.[C21] The electronic device according to any one of [C01] to [C20],wherein the second electrode is made of indium-gallium oxide,indium-doped gallium-zinc oxide, aluminum oxide-doped zinc oxide,indium-zinc oxide, or gallium-doped zinc oxide.[C22] The electronic device according to any one of [C01] to [C21],wherein the first electrode is made of indium-tin oxide, indium-zincoxide, or tin oxide.[C23] The electronic device according to any one of [C01] to [C22],wherein controlling an amount of introduced oxygen gas to form thesecond electrode by a sputtering method controls the value of the workfunction of the second electrode.[C24] The electronic device according to any one of [C01] to [C23],wherein a content rate of oxygen in the second electrode is less than acontent rate of oxygen in a stoichiometric composition.

REFERENCE SIGNS LIST

-   10 Substrate-   11 Wiring-   12 Insulating layer-   13 Opening-   21 First electrode-   22 Second electrode-   22A Second A layer in second electrode-   22B Second B layer in second electrode-   23 Light-receiving layer or light-emitting/light-receiving layer    (light-receiving layer or the like)-   30 Imaging element-   40 Solid-state imaging device-   41 Imaging area-   42 Vertical driving circuit-   43 Column signal processing circuit-   44 Horizontal driving circuit-   45 Output circuit-   46 Control circuit-   47 Vertical signal line-   48 Horizontal signal line-   101 Lens group-   102 Digital signal processor (DSP)-   103 Frame memory-   104 Display device-   105 Storage device-   106 Operating system-   107 Power supply system-   108 Bus line

What is claimed is:
 1. An imaging element comprising a laminatedstructure including a first electrode, a light-receiving layer formed onthe first electrode, and a second electrode formed on thelight-receiving layer, wherein the second electrode is made of atransparent amorphous oxide having a conductive property.
 2. The imagingelement according to claim 1, wherein assuming that a value of a darkcurrent flowing between the first electrode and the second electrode isJ_(d-0) (ampere) when 0 bolts are applied between the first electrodeand the second electrode, and assuming that a value of the dark currentflowing between the first electrode and the second electrode is J_(d-5)(ampere) when 5 bolts are applied between the first electrode and thesecond electrode, 0.8≦J_(d-5)/J_(d-0)≦1.2 is met.
 3. The imaging elementaccording to claim 1, wherein the laminated structure has an internalstress with compressive stress of MPa to 50 MPa.
 4. The imaging elementaccording to claim 1, wherein the second electrode has a surfaceroughness Ra of 1.5 nm or less and Rq of 2.5 nm or less.
 5. The imagingelement according to claim 1, wherein the second electrode has a workfunction of 4.5 eV or less.
 6. The imaging element according to claim 5,wherein the second electrode has a value of the work function of 4.1 eVto 4.5 eV.
 7. The imaging element according to claim 1, wherein thesecond electrode has an optical transmittance of 75% or more withrespect to light with wavelength of 400 nm to 660 nm.
 8. The imagingelement according to claim 1, wherein the second electrode has anelectric resistance value of 1×10⁻⁶Ω·cm or less.
 9. The imaging elementaccording to claim 1, wherein the second electrode has a thickness of1×10⁻⁸ m to 1.5×10⁻⁷ m.
 10. The imaging element according to claim 9,wherein the second electrode has the thickness of 2×10⁻⁸ m to 1×10⁻⁷ m.11. The imaging element according to claim 1, wherein the secondelectrode is made of a material formed by adding or doping at least onekind of material selected from the group consisting of aluminum,gallium, tin, and indium to one kind of material selected from the groupconsisting of indium oxide, tin oxide, and zinc oxide.
 12. The imagingelement according to claim 1, wherein the second electrode is made ofIn_(a)(Ga, Al)_(b)Zn_(c)O_(d).
 13. The imaging element according toclaim 12, wherein a difference between a value of a work function of thesecond electrode and a value of the work function of the first electrodeis 0.4 eV or more.
 14. The imaging element according to claim 13,wherein setting the difference between the value of the work function ofthe second electrode and the value of the work function of the firstelectrode to 0.4 eV or more generates an internal electric field in thelight-receiving layer on the basis of the difference in the values ofthe work functions and achieves improvement in internal quantumefficiency.
 15. The imaging element according to claim 12, wherein thesecond electrode has a laminated structure of a second B layer and asecond A layer from the light-receiving layer side, and a value of awork function of the second A layer in the second electrode is lowerthan a value of the work function of the second B layer in the secondelectrode.
 16. The imaging element according to claim 15, wherein adifference between the value of the work function of the second A layerin the second electrode and the value of the work function of the secondB layer in the second electrode is 0.1 eV to 0.2 eV.
 17. The imagingelement according to claim 15, wherein a difference between a value ofthe work function of the first electrode and the value of the workfunction of the second A layer in the second electrode is 0.4 eV ormore.
 18. The imaging element according to claim 15, wherein setting thedifference between the value of the work function of the first electrodeand the value of the work function of the second A layer in the secondelectrode to 0.4 eV or more generates an internal electric field in thelight-receiving layer on the basis of the difference in the values ofthe work functions and achieves improvement in internal quantumefficiency.
 19. A solid-state imaging device comprising a plurality ofimaging elements, wherein the imaging elements each have a laminatedstructure including a first electrode, a light-receiving layer formed onthe first electrode, and a second electrode formed on thelight-receiving layer, and the second electrode is made of a transparentamorphous oxide having a conductive property.
 20. An electronic devicecomprising a laminated structure including a first electrode, alight-emitting/light-receiving layer formed on the first electrode, anda second electrode formed on the light-emitting/light-receiving layer,wherein the second electrode is made of a transparent amorphous oxidehaving a conductive property.